Spatial and temporal variability of daily monsoon rainfall in Tunga and Bhadra River basins, Karnataka

Abstract

The Tropical Rainfall Measuring Mission (TRMM) rainfall product 3B42-V7 and the telemetric station data sets of years 2010 and 2011 for the monsoon season were used to study the spatial and temporal variability of the daily rainfall in Tunga and Bhadra River basins in Karnataka. The daily rain observations of gauge and TRMM estimates show correlation coefficient values of 0.63 for the stations located within the Western Ghats (highland) and 0.40 for the stations located away from the Western Ghats (midland). The threshold of 50% and 75% of the mean surface rainfall gives a good accuracy of 0.89 and 0.4 for midland stations and 0.62 for highland stations. The reliability of the TRMM data varies depending on the root mean square error of 10.74 mm in highland region and 5.25 mm in midland region. The amplitude of the variability is high over the highland stations; this may be due to the orography and the inconsistency in cell resolution of the satellite to that of the point data of the rain gauging stations. The variability in the diurnal time scale is also studied and it is found that high rainfall activity is in the afternoon hours in both the highland and midland regions. A bimodal variation during the active monsoon phase and unimodal variation during rest of the season is noticed in the highland region of the area, and unimodal variation in midland region is noticed throughout the south-west monsoon period.